Toyota Motor began facing complaints of runaway cars years ago, but the company did not install "brake override" systems in those vehicles, even as several other automakers deployed the technology to address such malfunctions.

The brake override systems allow a driver to stop a car with the footbrake even if the accelerator is depressed and the vehicle is running at full throttle. The systems are an outgrowth of new electronics in cars, specifically in engine control.

"If the brake and the accelerator are in an argument, the brake wins," a spokesman at Chrysler said in describing the systems, which it began installing in 2003.

Volkswagen, Audi, BMW and Mercedes-Benz also install such systems in at least some of their cars, the companies and industry experts said, some as far back as 10 years ago. General Motors installs brake override in all of its cars in which it is possible for the engine at full throttle to overwhelm the brakes.

"Most other automakers have adopted this technology," said Sean Kane, a former researcher at the Center for Auto Safety who now works at Safety Research and Strategies. Not adding the systems "is one of the mistakes that created this perfect storm for Toyota."

Toyota did not respond Thursday to questions about its decisions involving brake override.

But at the Detroit Auto Show in December, Toyota North America President Yoshi Inaba said the company would begin equipping its vehicles with brake override. His comments followed a November statement from the company that the override system would be made standard on Toyota and Lexus vehicles starting with some models in January 2010.

The precaution comes too late, however, to forestall a tsunami of negative publicity that has engulfed the company since it halted production and suspended sales of eight popular models after reports of unintended acceleration. For a company that famously aimed to become the largest automaker in the world by touting a reputation for reliability and safety, it has been a striking turnaround.

The company has blamed the accelerations on faulty floor mats and their installation, as well as defective accelerator pedals, which they are seeking to redesign. The brake override systems, when they come, will provide a measure of redundancy.

It was not immediately clear how much it would cost to install the brake override systems, and industry experts said the costs of the control technology are difficult to measure.

"There's really no cost, but it's a critical skill issue -- we can only find so many people who can do this kind of work," said a senior engineer at a major automaker, who spoke on the condition of anonymity. "It would require a bunch of software and development people to design it, but spread across lots of cars, the money involved would be negligible. . . . No one wants a runaway."

As far back as 2004, government investigators were looking at 2002-2003 Toyota Camrys and Solaras and Lexus ES 300s to determine whether they were defective, gathering information about 37 owner complaints of sudden acceleration, according to the Center for Auto Safety.

Automotive experts said that in at least some of those incidents, a brake override system could have prevented harm.

In the accident that has drawn perhaps the most publicity, a 2009 Lexus ES 350 raced through San Diego, weaving at 120 miles an hour through rush-hour freeway traffic. Veteran California Highway Patrol officer Mark Saylor was at the wheel, with his wife, teenage daughter and brother-in-law aboard.

"We're in trouble. . . . There's no brakes," Saylor's brother-in-law told a police dispatcher over a cellphone. As they approached an intersection, and the end of the road, the passengers could be heard urging each other to pray. All four died.

Afterward, investigators said that it appeared the brakes had been applied for so long that the brake pads melted, according to a report by the National Highway Traffic Safety Administration.

Had a brake override system been at work, the engine would have been depowered -- not turned off, but slowed.

Until recently, an accelerator pedal opened the throttle mechanically. But newer pedals control the engine via sensors and a computer.

The new throttle electronics and software have often themselves been the focus of some suspicion in the runaway crashes.

Whatever the causes of accidents, engineers noted that there are trade-offs in using brake override systems. For example, some customers prefer to be able to apply the brake and step on the accelerator without reducing power to the engine, especially in high-performance driving.

Toyota, moreover, is not the only automaker to eschew the fail-safe technology.

In an e-mail, Honda spokeswoman Christina Ra said that "Honda and Acura vehicles do not apply any override logic between brake and accelerator pedal inputs. . . . We continue to accept application of the accelerator and brake pedals as representing the driver's intention."

But experts said that the value of the brake override systems is that they can mitigate acceleration problems no matter where they come from. Toyota, as well as the NHTSA, appear to have struggled in diagnosing exactly what is causing the trouble.

"A brake override system can paper over a multitude of mistakes," Kane said.

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